Mesh / object mode with Pie menu?
You have to add the shortcut to the Object Mode shortcuts so it would be captured when you are in object mode, so the register function would be like this :

def register():
    bpy.utils.register_class(NewPie)
    #Add shortcuts
    wm = bpy.context.window_manager
    #Edit Mode    
    km = wm.keyconfigs.addon.keymaps.new(name="Mesh")
    kmi = km.keymap_items.new("wm.call_menu_pie", "E", "PRESS",shift=True, ctrl=True).properties.name="mypie"
    #Object Mode
    km = wm.keyconfigs.addon.keymaps.new(name="Object Mode")
    kmi = km.keymap_items.new("wm.call_menu_pie", "E", "PRESS", shift=True, ctrl=True).properties.name="mypie"